PURPOSE: To make it possible to perform multikind mixed production while performing almost circular application by closely contacting an application member with an application surface of a bulb to rotate the application member round an anode button as a center by means of a rotary driving device for applying an insulating agent around the button.

CONSTITUTION: When positioning of a bulb and supply of an insulating agent are finished, a robot 12 is transferred to the upper part of an anode button 5 according to a preinstructed program to rotate an application brush 17 while closely contacting the application surface of the bulb 4. At this time, when the upper and lower parts of the application surface are to be applied, the rotary axis 30 of the application brush is tilted to the side of application for performing application. By doing in this way, the brush 17 comes to close contact with the bulb 4 to further outside so as to prevent the application width from becoming small on the upper and lower part. By rotating the brush 17 in this way while rocking the rotary axis 30 up and down, the insulating agent can be applied around the anode button almost in an circular shape.